Internet Engineering Task Force M. Mawatari
Internet-Draft Japan Internet Exchange Co.,Ltd.
Intended status: BCP M. Kawashima
Expires: January 4, 2013 NEC AccessTechnica, Ltd.
C. Byrne
T-Mobile USA
July 3, 2012
464XLAT: Combination of Stateful and Stateless Translation
draft-ietf-v6ops-464xlat-05
Abstract
This document describes an architecture (464XLAT) for providing
limited IPv4 connectivity across an IPv6-only network by combining
existing and well-known stateful protocol translation RFC 6146 in the
core and stateless protocol translation RFC 6145 at the edge. 464XLAT
is a simple and scalable technique to quickly deploy limited IPv4
access service to IPv6-only edge networks without encapsulation.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 4, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Internet-Draft 464XLAT July 20121. Introduction
The IANA unallocated IPv4 address pool was exhausted on February 3,
2011. Each RIR's unallocated IPv4 address pool will exhaust in the
near future. It will be difficult for many networks to assign IPv4
addresses to end users, despite substantial IP connectivity growth
required for fast growing edge networks.
This document describes an IPv4 over IPv6 solution as one of the
techniques for IPv4 service extension and encouragement of IPv6
deployment. 464XLAT is not a one for one replacement of full IPv4
functionality. The 464XLAT architecture only supports IPv4 in the
client server model, where the server has global IPv4 address. This
means it is not fit for IPv4 peer-to-peer communication or inbound
IPv4 connections. 464XLAT builds on IPv6 transport and includes full
any to any IPv6 communication.
The 464XLAT architecture described in this document uses IPv4/IPv6
translation standardized in [RFC6145] and [RFC6146]. It does not
require DNS64 [RFC6147] since an IPv4 host may simply send IPv4
packets, including packets to an IPv4 DNS server, which will be
translated on the CLAT to IPv6 and back to IPv4 on the PLAT. 464XLAT
networks may use DNS64 [RFC6147] to enable single stateful
translation [RFC6146] instead of 464XLAT double translation where
possible. The 464XLAT architecture encourages IPv6 transition by
making IPv4 services reachable across IPv6-only networks and
providing IPv6 and IPv4 connectivity to single-stack IPv4 or IPv6
servers and peers.
By combining 464XLAT with BIH [RFC6535], it is also possible to
provide single IPv4 to IPv6 translation service, which will be needed
in the future case of IPv6-only servers and peers to be reached from
legacy IPv4-only hosts across IPv6-only networks.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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Internet-Draft 464XLAT July 2012
PLAT: PLAT is Provider side translator(XLAT) that complies with
[RFC6146]. It translates N:1 global IPv6 packets to global
IPv4 packets, and vice versa.
CLAT: CLAT is Customer side translator(XLAT) that complies with
[RFC6145]. It algorithmically translates 1:1 private IPv4
packets to global IPv6 packets, and vice versa. The CLAT
function is applicable to a router or an end-node such as a
mobile phone. CLAT SHOULD perform router function to
facilitate packets forwarding through the stateless
translation even if it is an end-node. In the case where the
access network does not allow for a dedicated IPv6 prefix for
translation, a NAT44 SHOULD be used between the router
function and the stateless translator function. The CLAT as
a common home router or 3G router is expected to perform
gateway functions such as DHCP server and DNS proxy for local
clients. The CLAT does not comply with the sentence "Both
IPv4-translatable IPv6 addresses and IPv4-converted IPv6
addresses SHOULD use the same prefix." that is described on
Section 3.3 in [RFC6052] due to using different IPv6 prefixes
for CLAT-side and PLAT-side IPv4 addresses.
4. Motivation and Uniqueness of 464XLAT
1. Minimal IPv4 resource requirements, maximum IPv4 efficiency
through statistical multiplexing
2. No new protocols required, quick deployment
3. IPv6-only networks are simpler and therefore less expensive to
operate
5. Network Architecture
464XLAT architecture is shown in the following figure.
5.1. Wireline Network Architecture
The private IPv4 host on this diagram can reach global IPv4 hosts via
translation on both CLAT and PLAT. On the other hand, the IPv6 host
can reach other IPv6 hosts on the Internet directly without
translation. This means that the CPE can not only have the function
of CLAT but also the function of IPv6 native router for IPv6 native
traffic.
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Internet-Draft 464XLAT July 2012
[I-D.hazeyama-widecamp-ipv6-only-experience].
6.2. Wireless 3GPP Network Applicability
The vast majority of mobile networks are compliant to Pre-Release 9
3GPP standards. In Pre-Release 9 3GPP networks, GSM and UMTS
networks must signal and support both IPv4 and IPv6 Packet Data
Protocol (PDP) attachments to access IPv4 and IPv6 network
destinations [RFC6459]. Since there are 2 PDPs required to support 2
address families, this is double the number of PDPs required to
support the status quo of 1 address family, which is IPv4.
464XLAT in combination with stateful translation [RFC6146] and DNS64
[RFC6147] allows 85% of the Android applications to continue to work
with single translation or native IPv6 access. For the remaining 15%
of applications that require IPv4 connectivity, the CLAT function on
the UE provides a private IPv4 address and IPv4 default-route on the
host for the applications to reference and bind to. Connections
sourced from the IPv4 interface are immediately routed to the CLAT
function and passed to the IPv6-only mobile network, destine to the
PLAT. In summary, the UE has the CLAT function that does a stateless
translation [RFC6145], but only when required. The mobile network
has a PLAT that does stateful translation [RFC6146].
464XLAT works with today's existing systems as much as possible.
464XLAT is compatible with existing network based deep packet
inspection solutions like 3GPP standardized Policy and Charging
Control (PCC) [TS.23203].
7. Implementation Considerations7.1. IPv6 Address Format
IPv6 address format in 464XLAT is defined in Section 2.2 of
[RFC6052].
7.2. IPv4/IPv6 Address Translation Chart7.2.1. Case of enabling only stateless XLATE on CLAT
This case should be used when a prefix delegation mechanism such as
DHCPv6-PD [RFC3633] is available to assign a dedicated translation
prefix to the CLAT.
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Internet-Draft 464XLAT July 20127.2.2. Case of enabling NAT44 and stateless XLATE on CLAT
This case should be used when a prefix delegation mechanism is not
available to assign a dedicated translation prefix to the CLAT. In
this case, NAT44 SHOULD be used so that all IPv4 source addresses are
mapped to a single IPv6 address.
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Internet-Draft 464XLAT July 20127.3. IPv6 Prefix Handling7.3.1. Case of enabling only stateless XLATE on CLAT
From the delegated DHCPv6 [RFC3633] prefix, a /64 is dedicated to
source and receive IPv6 packets associated with the stateless
translation [RFC6145].
The CLAT MAY discover the Pref64::/n of the PLAT via some method such
as DHCPv6 option, TR-069, DNS APL RR [RFC3123] or
[I-D.ietf-behave-nat64-discovery-heuristic].
7.3.2. Case of enabling NAT44 and stateless XLATE on CLAT
In the case that DHCPv6-PD [RFC3633] is not available, the CLAT does
not have dedicated IPv6 prefix for translation. If the CLAT does not
have a dedicated IPv6 prefix for translation, the CLAT can perform
with NAT44 and stateless translation [RFC6145].
Incoming source IPv4 packets from the LAN of [RFC1918] addresses are
NAT44 to the CLAT IPv4 host address. Then, the CLAT will do a
stateless translation [RFC6145] so that the IPv4 packets from the
CLAT IPv4 host address are translated to the CLAT WAN IPv6 address as
described in [RFC6052].
Its subnet prefix is made of the delegated prefix, completed if
needed to a /64 by a subnet ID = 0. Its interface ID is the 464XLAT
interface ID (Section 10).
The CLAT MAY discover the Pref64::/n of the PLAT via some method such
as TR-069, DNS APL RR [RFC3123] or
[I-D.ietf-behave-nat64-discovery-heuristic].
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Internet-Draft 464XLAT July 20127.4. Traffic Treatment Scenarios
+--------+-------------+-----------------------+-------------+
| Server | Application | Traffic Treatment | Location of |
| | and Host | | Translation |
+--------+-------------+-----------------------+-------------+
| IPv6 | IPv6 | End-to-end IPv6 | None |
+--------+-------------+-----------------------+-------------+
| IPv4 | IPv6 | Stateful Translation | PLAT |
+--------+-------------+-----------------------+-------------+
| IPv4 | IPv4 | 464XLAT | PLAT/CLAT |
+--------+-------------+-----------------------+-------------+
| IPv6 | IPv4 | Stateless Translation | CLAT |
+--------+-------------+-----------------------+-------------+
Traffic Treatment Scenarios
The above chart shows most common traffic types and traffic
treatment.
7.5. DNS Proxy Implementation
The CLAT SHOULD implement a DNS proxy as defined in [RFC5625]. The
case of an IPv4-only node behind CLAT querying an IPv4 DNS server is
undesirable since it requires both stateful and stateless translation
for each DNS lookup. The CLAT SHOULD set itself as the DNS server
via DHCP or other means and proxy DNS queries for IPv4 and IPv6
clients. Using the CLAT enabled home router or UE as a DNS proxy is
a normal consume gateway function and simplifies the traffic flow so
that only IPv6 native queries are made across the access network.
The CLAT SHOULD allow for a client to query any DNS server of its
choice and bypass the proxy.
7.6. CLAT in a Gateway
The CLAT is a stateless translation feature which can be implemented
in a common home router or mobile phone that has a mobile router
feature. The router with CLAT function SHOULD provide common router
services such as DHCP of [RFC1918] addresses, DHCPv6, and DNS
service. The router SHOULD set itself as the DNS server advertised
via DHCP or other means to the clients so that it may implement the
DNS proxy function to avoid double translation of DNS request.
7.7. CLAT to CLAT communications
While CLAT to CLAT IPv4 communication may work when the client IPv4
subnets do not overlap, this traffic flow is out of scope. 464XLAT is
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Internet-Draft 464XLAT July 2012
a hub and spoke architecture focused on enabling IPv4-only services
over IPv6-only access networks.
8. Deployment Considerations
Even if the Internet access provider for consumers is different from
the PLAT provider (e.g. another internet access provider), it can
implement traffic engineering independently from the PLAT provider.
Detailed reasons are below:
1. The Internet access provider for consumers can figure out IPv4
destination address from translated IPv6 packet header, so it can
implement traffic engineering based on IPv4 destination address
(e.g. traffic monitoring for each IPv4 destination address,
packet filtering for each IPv4 destination address, etc.). The
tunneling methods do not have such a advantage, without any deep
packet inspection for processing the inner IPv4 packet of the
tunnel packet.
2. If the Internet access provider for consumers can assign IPv6
prefix greater than /64 for each subscriber, this 464XLAT
architecture can separate IPv6 prefix for native IPv6 packets and
XLAT prefix for IPv4/IPv6 translation packets. Accordingly, it
can identify the type of packets ("native IPv6 packets" and
"IPv4/IPv6 translation packets"), and implement traffic
engineering based on IPv6 prefix.
This 464XLAT architecture has two capabilities. One is a IPv4 ->
IPv6 -> IPv4 translation for sharing global IPv4 addresses, another,
if combined with BIH [RFC6535], is a IPv4 -> IPv6 translation for
reaching IPv6-only servers from IPv4-only clients that can not
support IPv6. IPv4-only clients must be support through the long
period of global transition to IPv6.
9. Security Considerations
To implement a PLAT, see security considerations presented in Section5 of [RFC6146].
To implement a CLAT, see security considerations presented in Section7 of [RFC6145]. The CLAT MAY comply with [RFC6092].
10. IANA Considerations
IANA is requested to reserve a Modified EUI-64 identifier for 464XLAT
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Internet-Draft 464XLAT July 2012Appendix A. Examples of IPv4/IPv6 Address Translation
The following are examples of IPv4/IPv6 Address Translation on the
464XLAT architecture.
Example 1. (Case of enabling only stateless XLATE on CLAT)
In the case that IPv6 prefix greater than /64 is assigned to end
users by such as DHCPv6-PD [RFC3633], only the function of Stateless
XLATE should be enabled on CLAT. Because the CLAT can use dedicated
a /64 from the assigned IPv6 prefix for Stateless XLATE.
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